Every puzzle in this app is a 27-clue grid with exactly one solution — verified in advance, so there's always a logical path through, never a guess required. "Extreme" is the hardest tier in this app by a real measure, not just by name: every single puzzle requires a full alternating inference chain (X-Cycle, XY-Chain, or AIC) before it gives way — nothing here stops at Wings or colouring. On average that's about 17 non-Singles moves per puzzle, which is actually higher than "Diabolical"'s average of 12. If you've cleared every other difficulty, this is the real test.
Paste 81 numbers, in almost any format: comma- or space-separated, a 9×9 grid, or one long string. Use 0 or . for empty cells — box-drawing separators (| and ---+---) are fine too.
Solved in 00:00:00 with 0 mistakes and 0 clues used.
Congratulations — solved in 00:00:00. Would you like to play again?
This ends your current game — progress won't be saved.